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*blackedoutharley* · 11-29-2011, 03:26 AM

The SM420 input shaft is 1 1/8 x 10 spline.

There is another unit called a "brownie" but I can't remember how it mounts. I agree the GearVendors unit is probably the easiest OD unit as far as installation.

11-29-2011, 03:26 AM	#12
blackedoutharley Account Suspended Join Date: Jul 2007 Location: Plumas Lake, Ca. Posts: 1,009	Re: Overdrive help for my SM420 The SM420 input shaft is 1 1/8 x 10 spline. There is another unit called a "brownie" but I can't remember how it mounts. I agree the GearVendors unit is probably the easiest OD unit as far as installation.